We’ve all been there, done that: "Ahhh." But did you know that scratching one part of the body is more pleasurable than scratching another? And no, not your first thought. Lower. Try the ankles.

Actually, the authors of the new paper didn’t study the “private” region, “a totally different ball game,” says co-author Gil Yosipovitch, MD, founder of the International Forum for the Study of Itch. For one, Yosipovitch says, psychological factors probably help determine how pleasurable it is to scratch that part of the body.

Yosipovitch, a dermatology professor at Wake Forest Baptist Medical Center, and his co-authors compared itching and scratching on the back, forearm, and ankle -- and they say they are the first to report the pleasurability of scratching an itch on different parts of the body.

Most itch research has focused only on the easy-to-study forearm, ignoring the fact that the back is well-known to be a preferred site for scratching, as evidenced by the centuries-long popularity of back-scratchers, Yosipovitch says.

The back, forearm, and ankle are all common sites of scratching in lichen simplex chronicus, a skin condition that is associated with chronic itching and scratching, which in turn leads to thickening of the skin. Lichen simplex chronicus sometimes occurs in people with eczema, psoriasis, or disorders such as anxiety or depression.

Yosipovitch and his co-authors recruited 18 healthy adult volunteers who didn’t have any itch-provoking conditions. Researchers induced an itch on their backs, forearms, and ankles by gently rubbing tiny, pointed pieces from a tropical legume known to cause intense itching into their skin.

They then asked the volunteers to rate the intensity of the itch on a scale of 1 to 10 at 30-second intervals.

Scratching That Itch

In the next phase of the study, an investigator used a tiny brush to scratch the itch immediately after it was induced. The volunteers were asked to rate the intensity of the itch and the pleasurability of scratching on a scale of 1 to 10, again at 30-second intervals.

The scientists found that, on average, itch intensity and scratching pleasurability were significantly higher at the ankle and back than on the forearm. At the back and forearm, scratching pleasurability declined in line with the itch reduction. But at the ankle, the itchiest site of all, scratching continued to feel oh-so-good even as the itch intensity diminished.

Yosipovitch and his co-authors say they aren’t sure why. Previous research has shown that nerve density is lower, not higher, in the legs, so that wouldn’t explain why both itch intensity and scratching pleasure were greatest at the ankle. And, Yosipovitch notes, the face is full of nerves, yet people don’t often complain of itchy foreheads or cheeks.

His goal, he says, is to develop a treatment that can induce the pleasurable relief of a scratch without damaging the skin.

If reading about Yosipovitch’s research makes you feel like scratching, he probably wouldn’t be surprised. He published a study last year that found scratching, like yawning, is contagious.

Yosipovitch and his co-authors published their new findings online in the British Journal of Dermatology.